CVE-2026-55489 in BigBlueButton
Summary
by MITRE • 08/21/2026
BigBlueButton is an open-source virtual classroom. Prior to 3.0.29, BigBlueButton presenters could submit a presentationId through /api/graphql that identified a presentation belonging to another meeting. akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/presentationpod/RemovePresentationPubMsgHdlr.scala did not verify the presentation's meeting identifier before deletion, allowing a presenter who knew the identifier to delete another meeting's presentation and disrupt its availability. This issue is fixed in version 3.0.29.
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Analysis
by VulDB Data Team • 08/24/2026
The vulnerability identified in BigBlueButton versions prior to 3.0.29 represents a critical failure in access control mechanisms within the application's GraphQL API layer. Specifically, the endpoint responsible for handling presentation removal requests failed to enforce proper authorization checks regarding the association between the authenticated user and the target resource. In a typical secure implementation of such systems, any operation that modifies or deletes data must verify that the requesting entity possesses explicit permission relative to the specific instance being acted upon. However, in this flawed architecture, the handler logic located at akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/presentationpod/RemovePresentationPubMsgHdlr.scala accepted a presentation identifier from the client without cross-referencing it against the meeting context associated with the presenter's active session or token. This oversight created an opportunity for unauthorized modification of shared resources, undermining the integrity and availability guarantees expected in collaborative virtual classroom environments.
From a technical perspective, this flaw is classified as an Insecure Direct Object Reference (IDOR), which corresponds to CWE-639 in the Common Weakness Enumeration standard. The vulnerability arises because the application relies on client-supplied identifiers to perform server-side actions without validating that these identifiers belong to resources owned or authorized for access by the current user session. An attacker, defined here as any authenticated presenter within the BigBlueButton ecosystem who is aware of valid presentation identifiers from other meetings, could exploit this logic error. By crafting a malicious GraphQL query containing the target presentationId, the actor can trigger the deletion routine on the server side. The system processes the request and removes the specified presentation data without confirming that the requester has any legitimate relationship to the meeting in which that presentation resides. This lack of object-level authorization control allows for arbitrary resource manipulation based solely on knowledge of an identifier rather than proper permission validation.
The operational impact of this vulnerability is significant, primarily affecting the availability and reliability of virtual classroom sessions. Since BigBlueButton serves as a platform for education and remote collaboration, the disruption caused by unauthorized deletion of presentations can halt instructional activities or cause substantial confusion during live meetings. Presenters may lose access to their prepared materials mid-session if an adversary targets them with this exploit. Furthermore, because the vulnerability allows any presenter to affect other meetings, it introduces a risk of cross-meeting interference that could be used for malicious disruption rather than accidental error. This compromises the trust model inherent in multi-tenant SaaS or on-premise deployments where distinct groups rely on isolated and stable environments. The ability to delete another meeting's presentation constitutes a denial-of-service condition specific to critical assets, potentially requiring administrative intervention to restore lost data if backups are not immediately available.
To mitigate this vulnerability, organizations running BigBlueButton must upgrade to version 3.0.29 or later, where the developers have implemented proper authorization checks in the removal handler logic. This fix ensures that before a presentation is deleted, the system verifies that the presenter initiating the request belongs to the same meeting context as the target presentation. Additionally, security best practices dictate implementing robust input validation and enforcing strict access control policies at every layer of the application stack. Developers should adopt principle of least privilege when designing API endpoints, ensuring that each operation validates both user identity and resource ownership before executing state-changing commands. Regular penetration testing focused on broken object level authorization can help identify similar flaws in other parts of the platform. Monitoring logs for unusual patterns of presentation deletions across different meetings may also provide early detection indicators if such vulnerabilities were to emerge in future versions or unpatched deployments.